This invention relates to a process for anionically polymerizing vinyl monomers.
It is known that alkali metals form compounds with graphite and that these intercalation compounds can be used to polymerize vinyl monomers. (G. Merle, J. P. Pascault, Q. T. Pham, C. Pillot, R. Salle, J. Gole, I. Rashkov, I. Panayotov, D. Guerard and A. Herold, J. Poly. Sci. Poly. Chem., 15, pp 2067-2074 (1977)).
Also graphite has been electrochemically reduced by Simonet and Lund and independently by Besenhard. They independently prepared reduced graphite by electrolytically reducing graphite in a polar aprotic solvent containing an electrolyte, thus, preparing the graphite anion with a quaternary ammonium cation or alkali metal cation associated with the anion and intercalated in the graphite. Simonet and Lund demonstrated that this reduced graphite containing graphite anion radical quaternary ammonium cation could function as an electron-transfer agent by showing that fluorenone could be reduced with anion radical. (J. Simonet and H. Lund, J. Electroanal. Chem., 75, pp. 719-730 (1977) and J. O. Besenhard, Carbon, 14 pp. 111-115 (1976)).
Normally in electrolytic polymerization processes it is necessary to reduce a monomer in the presence of electrolyte salt and solvent, and then a tedious and costly work-up is involved in freeing the polymer from both the electrolyte salt and solvent; whereas, the process of the invention permits preparation of polymer free of electrolyte salt and, in some cases, even free of solvent.
The prior art process described herein on page 1, lines 6-9, produces anionic intermediates with alkali metal counterions; whereas, the process of this invention provides R.sub.4 N.sup.+ counterions which have not previously been achieved with non-electrochemical means. The reactivity iof M.sup.+ R.sup.- polymer backbone R.sup.- M.sup.+ where M is alkali metal is different from that of R.sub.4 N.sup.+ R.sup.- polymer backbone R.sup.- R.sub.4 N.sup.+ both with respect to rates of reaction and possibly even stereochemistry. Furthermore, whereas electron-transfer from Graphite M.sup.+ to a vinyl monomer occurs readily if the vinyl monomer has not a very negative reduction potential; the electron-transfer from Graphite R.sub.4 N.sup.+ can occur even to a monomer of very negative reduction potential.
Also, anionic block copolymers can be formed by the process of the invention using a mixture of two or more different monomer, such as styrene and butadiene or styrene and ethylene oxide; alternatively, the second monomer will not be initially present but is added after the first monomer has been polymerized. More details with regard to other suitable monomer combinations and block copolymerization and found in chapter 3, Block Copolymers, W. H. Janes and D. C, Allport, eds., J. Wiley and Sons, 1973.